U.S. patent number 5,437,717 [Application Number 08/258,935] was granted by the patent office on 1995-08-01 for asphalt compositions with improved cross-linking agent.
This patent grant is currently assigned to Vinzoyl Petroleum Co.. Invention is credited to Michael P. Doyle, Jimmy L. Stevens.
United States Patent |
5,437,717 |
Doyle , et al. |
August 1, 1995 |
Asphalt compositions with improved cross-linking agent
Abstract
An improved, substantially anhydrous, cross-linking agent is
disclosed for use in asphalt compositions of the type used for
roofing and paving materials. The cross-linking agent comprises a
blend of tall oil, a strong base, n-methyl fatty acid taurate, and
fatty amines and is substantially free of water.
Inventors: |
Doyle; Michael P. (Phoenix,
AZ), Stevens; Jimmy L. (Rio Linda, CA) |
Assignee: |
Vinzoyl Petroleum Co. (Phoenix,
AZ)
|
Family
ID: |
22982762 |
Appl.
No.: |
08/258,935 |
Filed: |
June 13, 1994 |
Current U.S.
Class: |
106/220; 106/229;
106/284.4 |
Current CPC
Class: |
C08L
95/00 (20130101); C10C 3/026 (20130101); C08L
95/00 (20130101); C08L 2666/26 (20130101) |
Current International
Class: |
C08L
95/00 (20060101); C10C 3/02 (20060101); C10C
3/00 (20060101); C09D 195/00 (); C09D 007/12 ();
C08L 093/00 (); C08L 091/00 () |
Field of
Search: |
;106/220,229,284.4 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4450011 |
May 1984 |
Schilling et al. |
4806166 |
February 1989 |
Schilling et al. |
4859245 |
August 1989 |
Schilling et al. |
|
Primary Examiner: Brunsman; David
Attorney, Agent or Firm: Vinson & Elkins
Claims
We claim:
1. An improved cross-linking agent for asphalt compositions, said
cross-linking agent comprising:
tall oil;
a strong base;
n-methyl fatty acid taurate; and
fatty amines;
said cross-linking agent being substantially free of water.
2. The cross-linking agent according to claim 1, wherein said tall
oil comprises from about 50 to about 80 weight percent of said
cross-linking agent.
3. The cross-linking agent according to claim 1 wherein said strong
base comprises from about 10 to about 25 weight percent of said
cross linking agent.
4. The cross-linking agent according to claim 1 wherein said
n-methyl fatty acid taurate comprises from about 5 to about 25
weight percent of said cross linking agent.
5. The cross-linking agent according to claim 1 wherein said fatty
amines comprise from about 1 to about 20 weight percent of said
cross-linking agent.
6. An asphalt composition having improved adhesion to aggregate,
said composition comprising:
asphalt and an adhesion improving amount of a cross-linking
agent;
said cross-linking agent comprising the reaction product of tall
oil, a strong base, n-methyl fatty acid taurate and fatty
amines.
7. The asphalt composition according to claim 6 wherein said
cross-linking agent is substantially free of water.
8. The asphalt composition according to claim 6 wherein said
cross-linking agent comprises from about 1 to about 6 weight
percent of said composition.
9. An asphalt composition having improved adhesion to crumb rubber
from used automobile tires, said composition comprising asphalt and
an adhesion improving amount of a cross-linking agent; said
cross-linking agent comprising the reaction product of tall oil, a
strong base, n-methyl fatty acid taurate and fatty amines and being
substantially free of water.
10. The asphalt composition according to claim 9 wherein said
cross-linking agent comprises from about 1 to about 6 weight
percent of such composition.
11. An asphalt composition comprising:
asphalt;
crumb rubber from used automobile tires; and
an adhesion improving amount of a cross-linking agent comprising
tall oil, a strong anhydrous base, n-methyl fatty acid taurate and
fatty amines, said cross-linking agent being substantially free of
water.
12. A method for preparing an asphalt composition, said process
comprising:
blending with an asphalt an adhesion improving amount of a
cross-linking agent comprising the reaction product of tall oil, an
anhydrous strong base, n-methyl fatty acid taurate and fatty amines
to provide a first mixture; and
blending with said first mixture crumb rubber from used automobile
tires to provide a second mixture.
13. The method according to claim 12 wherein said first mixture
includes from about 1 to about 6 weight percent of cross-linking
agent, based upon the weight of said first mixture and wherein said
second mixture comprises from about 5 to about 25 weight percent of
crumb rubber, based upon the weight of said second mixture.
Description
FIELD OF THE INVENTION
This invention relates to asphalt compositions of the type utilized
for roofing and paving materials, as well as to processes for their
preparation, characterized by the use of an improved cross-linking
agent produced by the anhydrous saponification of tall oil.
BACKGROUND OF THE INVENTION
Asphalt (or bitumen) compositions are in widespread use as
asphalt-aggregate blends for road paving, in roofing shingles, in
hot applied asphalt roofing systems, and similar applications. A
problem with such compositions is their tendency to become brittle
at low temperatures and to become soft at high temperatures.
Various additives, polymers, etc., have been utilized for the
purpose of improving the high and low temperature characteristics
of asphalt compositions, as well as to .improve their toughness and
durability. Tall oil, produced primarily as a byproduct of certain
paper manufacturing processes, is widely used for this purpose,
both as a direct additive and in its various modified forms,
including saponified tall oil. However, most prior art processes
for tall oil saponification have utilized added water (usually as a
component of a caustic solution used in the saponification process)
with the result that the saponified tall oil product often has a
high water content. Water is deleterious to high temperature
asphalt blending processes, since the water flashes off, resulting
in the swelling of the asphalt, production of large quantities of
steam vapor containing entrained light end components, leaching of
hydrocarbons from the asphalt, etc. The prior art therefore
discloses various attempts to produce asphalt blends, or other tall
oil containing compositions utilizing a minimum of added water.
Another limitation of the prior art has been a limit on the amount
of saponified tall oil capable of being kept in solution with
asphalt. Prior art methods did not address tall oil-asphalt
compatibility.
U.S. Pat. No. 5,221,703 entitled "Engineered Modified Asphalt
Cement" relates to a modified bituminous material containing
asphalt, tall oil, a polymer (such as styrene butidiene, natural
latex, etc.) and a strong base (preferably sodium hydroxide or
potassium hydroxide). A small amount of water is present in the
composition, either as water in a solution of the strong base, or
water in a latex added as the polymer in the composition.
U.S. Pat. No. 1,81.3,454 entitled "Saponification" discloses a
process for saponifying organic esters, particularly the esters of
fatty acids, such as vegetable and animal fats. The process
comprises treating the organic ester with substantially anhydrous
alkali in the presence of an inert organic diluent in which the
alcoholic component of the ester is substantially insoluble, and
simultaneously removing the alcoholic component in a concentrated
form by partial pressure distillation of the diluent and the
alcoholic component.
U.S. Pat. No. 2,268,122 entitled "Road Tars or the Like and the
Methods of Making Them" also discloses a process for substantially
anhydrous saponification of fatty oils using an organic diluent
such as kerosene.
U.S. Pat. No. 2.753.363 entitled "Method of Making Soap" relates to
the manufacture of soap, and more particularly to an improved
method of making a soap of relatively low moisture content wherein
the saponification is carried out in two stages. In the first
stage, a fatty acid mixture, or a mixture of fatty acids and
glycerides, is reacted with a quantity of dry alkali metal
carbonate that is sufficient to saponify a substantial proportion
of the free fatty acids present in the raw material but
insufficient to saponify all of the .fatty materials present.
Thereafter, in a second stage, saponification of the fatty material
is completed with a concentrated aqueous caustic alkali.
U.S. Pat. No. 4,129,520 entitled "Soap Making" discloses a process
for saponifying organic acid esters in fats from animal or
vegetable sources in which process the organic acid esters are
saponified with alkali metal hydroxide in a liquid reaction medium
comprising a substantially water-free alkyl nitrile. The preferred
anhydrous reaction media are acetonitrile and proprionitrile. The
stated advantage of the anhydrous preparation method is that the
solvent removal is less energy intensive than in aqueous processes.
The preferred products of the process are soaps and detergents.
U.S. Pat. No. 4,874,432 entitled "Multigrade Asphalt Cement Product
and Process" relates to a process for producing a multi-grade
asphalt cement product. The process involves saponifying in
liquefied asphalt, substantially free of water, at least one fatty
acid and at least one resin acid with an alkali metal base, or by
adding the already saponified acid to the liquefied asphalt. The
resulting gelled asphalt cement is utilized in conventional
processes for road paving, roofing, and specialty applications. The
preferred organic acid component for the process is tall oil and
the preferred alkali metal base is anhydrous sodium hydroxide.
A secondary feature of the asphalt compositions of the present
invention is their ability to incorporate substantial amounts of
crumb rubber from used automobile tires. A significant ecological
problem is presented in the U.S. by the accumulation of used
automobile tire carcasses which are very difficult to dispose of or
to recycle into other uses. Various proposals have been made for
incorporating crumb rubber from shredded used tires into asphalt
paving compositions. However, the vulcanizing process used in
manufacturing the tires, as well as the presence of various
fillers, plasticizers, elastomers and other ingredients in the
tires, make it very difficult to successfully incorporate crumb
rubber from used tires into paving compositions. When blended into
asphalt concrete compositions, the vulcanized rubber particles do
not easily bond to the asphalt cement, and tend to separate from
the composition. PCT International Publication WO93/17076 entitled
"Asphalt Composition and Process for Obtaining Same," and the prior
art patents and publications discussed therein, disclose a variety
of prior art attempts to successfully incorporate ground rubber
from automobile fires into asphalt paving or roofing compositions.
Such efforts have not been commercially successful.
SUMMARY OF THE INVENTION
It is, accordingly, the primary object of the present invention to
provide an improved cross-linking agent for asphalt compositions,
characterized by the anhydrous saponification of tall oil. This
improved cross-linking agent contains a tall oil-asphalt
compatabilizer. This compatabilizer allows high percentages of
saponified tall oil to be added to asphalt without separation
occurring. Prior art methods would not allow these high
percentages. This allows the asphalt to be modified to achieve
extreme properties.
Another object is to provide asphalt compositions utilizing such
cross-linking agent which demonstrate improved high and low
temperature performance characteristics, as well as improved
adhesion and overall wear characteristics.
A further object is to provide such improved asphalt compositions
which incorporate substantial amounts of crumb rubber from used
automobile tires and in which such crumb robber is successfully
maintained in suspension.
A further object is to provide such asphalt compositions which meet
SHRP ("Strategic Highway Research Program") specifications, without
the use of expensive, high polymer content in the compositions, as
well as to provide asphalt compositions incorporating crumb rubber
which meet SHRP specifications.
A further object is to provide asphalt compositions which meet the
requirements for use in roofing applications without requiring that
the asphalt be air blown.
As discussed more fully in the detailed disclosure below, these
objects and advantages of the invention are accomplished by
producing an improved cross-linking agent for asphalt compositions
characterized by the anhydrous saponification of tall oil utilizing
a dry caustic dissolved in an organic solvent. The caustic fully
dissolves in the solvent and does not require shearing as in other
inventions. The resulting anhydrous saponified tall oil product
demonstrates superior additive effect in converting asphalt
compositions to non-Newtonian flow characteristics, as compared to
prior art aqueous saponified tall oils, thereby improving their
high temperature and low temperature performance characteristics.
Asphalt compositions incorporating the anhydrous saponified tall
oil cross-inking agent also demonstrate superior performance in
their ability to adhere to aggregate and to retain in suspension
crumb rubber from pulverized automobile tires. No prior art asphalt
additive has demonstrated a satisfactory ability to adhere to and
to retain such crumb rubber components in suspension in asphalt
paving mixtures.
DETAILED DISCLSOURE
The improved asphalt cross-linking agent of the invention is
prepared by saponifying tall oil in a strong anhydrous base. Tall
oil is a natural mixture of rosin acids and fatty acids, together
with unsaponifiable materials, which is obtained in commercial
quantities by acidifying the black liquor skimmings of the sulfate
process of wood pulp manufacture or kraft paper manufacture, using
resinous woods such as pine. The composition of tall oil varies
somewhat depending upon such factors as the species of the wood
which was pulped. Tall oil made from trees in northern U.S. states,
such as Michigan, Wis., and Minnesota, tends to have a higher rosin
acid content. Crude tall oil acids generally will contain 18% to
60% fatty acids, 28% to 66% rosin acids and 3% to 24% unsaponified
materials.
For the purpose of this invention, crude tall oil acids may be
used; however, it is preferable to use distilled tall oil. The
distillation may be carried out by introducing crude tall oil into
a fractionation unit to separate the volatile fraction of crude
tall oil from the nonvolatile or pitch. Except for some separation
of palmitic and more volatile acids in the first fraction, tall oil
distillates have nearly the same composition as the crude tall oil.
A typical tall oil distillate may contain from 30% to 66% rosin
acids, from 37% to 52% tall oil acids and from 3% to 12%
unsaponifiable materials. Various ratios of fatty acid to rosin
acid may be used.
The fatty acid fraction contains saturated and unsaturated fatty
acids and the rosin acid fraction contains a number of different
rosin acids with the greatest portion concentrated in the following
typical analysis which is intended to be suggestive and not
limited.
______________________________________ Percent
______________________________________ Fatty Acid Fraction
Saturated acids 7.8 Oleic acid 39.2 Linoleic acid 26.1 Conjugated
dienoic acids 15.4 Other fatty acids 11.5 Rosin Acid Fraction
Dihydropimaric 2.0 Primaric type 13.6 Dihydroabietic 3.8 Palustric
9.2 Abietic 43.8 Dehydroabietic 21.4 Neoabietic 6.2 100.0
______________________________________
The unsaponifiable materials consist mainly of hydrocarbons, high
molecular weight alcohols, primarily sterols, and small quantities
of degradation products of lignin compounds. Small quantities of
water, on the order of 2% to 3%, also commonly are present in crude
tall oil. For purposes of the present invention, it is preferred
that tall oil used in preparing the cross-linking agent first be
heated to a temperature sufficiently high to assure that all water,
if any, contained in the tall oil has been removed.
As used herein, "tall oil" means tall oil, tall oil pitch, tall oil
derivatives, or mixtures of any two or more of these, unless
otherwise specifically stated.
The anhydrous strong base used to saponify the tall oil is prepared
by solubilizing anhydrous sodium hydroxide in a non-aqueous
solvent. The preferred solvent is an n-methyl fatty acid taurate
(sold under the trade name "Polyfac TT-3" by Westvaco Chemicals,
Charleston Heights, South Carolina) to form a solution containing
sodium salts of taurate. An additional proprietary product,
comprising a blend of various fatty amines (sold under the
trademark "Catamine 101" by Exxon Chemical Americas, Miton,
Wisconsin) preferably also is added, since it improves subsequent
saponification of the tall oil and compatabilizes the tall oil with
the asphalt.
When the resulting strong base is blended with crude tall oil, the
fatty rosin acids in the crude tall oil are saponified to form a
soft soap which has a high affinity for the polar compounds in
asphalt and acts as a binding agent in asphalt blends. As a result,
the asphalt blends are converted from Newtonjan to non-Newtonian
flow characteristics.
A preferred composition for the cross-linking agent is: crude tall
oil 71 weight percent; anhydrous sodium hydroxide 13 weight
percent; n-methyl fatty acid taurate (Polyfac TT-3), 8 weight
percent; fatty amines (Catamine 101), 8 weight percent. However,
the exact composition may vary widely within the general range of
tall oil being 50 weight percent to 80 weight percent; anhydrous
sodium hydroxide 10 weight percent to 25 weight percent; n-methyl
fatty acid tautate 5 weight percent to 25 weight percent; and fatty
amines 1 weight percent to 20 weight percent. If desired, in lieu
of the Catamine 101, any other polyamine or fatty amine mixture may
be substituted. Similarly, Polyfac TT-3 may be replaced by other
anhydrous organic solvents or surfactants suitable for solubilizing
metal salts, such as, for example, Witco AE-7 (quatanary ammonium
chloride).
In the preferred order of addition and blending of the components
for the cross-linking agent, anhydrous sodium hydroxide beads are
added to the Polyfac TT-3 with continuous stirring. The addition of
the caustic raises the temperature to approximately 165.degree. F.
Stirring continues until the caustic is solubilized. The Catamine
101 is then added while a small amount of heat is applied to
maintain 160.degree. F. to 180.degree. F. The resulting mixture is
then blended with water-free crude tall oil (at about 220.degree.
F.) with stirring and continued heating (to about 240.degree. F.)
until the exothermic saponification reaction is completed (about 10
minutes). The resulting saponified tall oil cross-linking agent is
then blended immediately with hot asphalt or bitumen, which may
contain other ingredients (aggregate, crumb rubber, other
additives, etc.) to produce the final product.
The amount of cross-linking agent blended with the asphalt will
vary widely, depending upon the intended application. However,
generally from about 1 weight percent to about 6 weight percent of
cross-linking agent will be used, based upon the combined weight of
the asphalt/cross-linking agent blend.
When crumb rubber/asphalt blends are created, the asphalt is first
heated to between 375.degree. F. to 490.degree. F., but more
preferably, about 400.degree. F. The crumb rubber is added at
between 5 weight percent and 25 weight percent based on asphalt
weight, depending on the desired properties. A high shear mill is
used to reduce the size of the rubber which may be from 10 mesh to
80 mesh with 30 mesh being preferred. The crumb rubber and asphalt
are sheared 1 to 3 hours with 2 hours being preferred. The
asphalt/rubber composition temperature is lowered to 375.degree. F.
and the cross-linking agent added at between 1 weight percent and 6
weight percent, with 3.5 weight percent preferred, based on total
composition weight. Aromatic oils may also be added to maintain the
original asphalt internal chemistry and aid in digesting the crumb
rubber.
EXPERIMENTAL
To demonstrate the improvements of the present invention, a series
of asphalt batches were prepared and tested, with and without the
anhydrous saponified tall oil cross-linking agent. The
cross-linking agent used in the experiments was prepared in
accordance with the following formula:
______________________________________ Weight Percent Component
______________________________________ 71 Crude Tall Oils 12.8
Anhydrous Sodium Hydroxide 8.1 Polyfac TT-3 8.1 Catamine 101
______________________________________
The method of preparation of the cross-linking agent is as
procedure disclosed above.
The compositions of the test batches, and their methods of
preparation were as follows, test results are listed in Tables 1
and 2:
1. AC-5. This is a standard asphalt meeting AASHTO M226-80 Table II
for AC-5.
2. AC-5+3.3 Weight Percent CLA, Based on Asphalt Weight. The
asphalt in No. 1 above is heated to 375 .degree. F. While
maintaining 375 .degree. F., 3.3 weight percent CLA is added and
stirred in. Once all the CLA is solubilized in asphalt, stir for 10
to 15 minutes to cross link the asphalt. Then test.
3. AC-5+10 Weight Percent Tire Rubber ("TR")+2 Weight Percent Oil,
Based on Asphalt Weight. Heat AC-5 plus oil to 400 .degree. F. and
add TR while applying high shear for 2 hours. Placed in oven at
350.degree. F. overnight. After 24 hours, TR had settled to bottom
of container. No tests run.
4. AC-5+10 Weight Percent TR+2 Weight Percent Oil, Based on Asphalt
Weight. Same as above procedure but high sheared at 490.degree. F.
instead of 400.degree. F. Checked for settlement. After 24 hours,
three-quarters of TR settled out. No tests run.
5. AC-5+3.3 Weight Percent CLA+10 Weight Percent TR+2 Weight
Percent Oil, Based on Asphalt Weight. Asphalt is heated and 2
weight percent aromatic oil (raffex 170) is added). The asphalt and
oil mixture is heated to 400.degree. F. 30 mesh crumb rubber from
Baker Rubber is then added and high sheared using a Silverson Mixer
for 2 hours. The rubber asphalt mixture is inspected for smoothness
and, if needed, sheared longer. Once smooth, the temperature of the
mixture is lowered to 375.degree. F. and 3.3 weight percent CLA
added using stirring for 15 minutes or so. The mixture is then
tested for the desired properties, including settlement of
rubber.
6. AC-10, meeting AASHTO M226-80 Table I.
7. AC-10+2 Weight Percent CLA, Based on Asphalt Weight.
8. AC-10+3.3 Weight Percent CLA, Based on Asphalt Weight. See
procedure outlined in 2 above.
9. AC-10+3.3 Weight Percent CLA+10 Weight Percent Crumb Tire
Rubber+2 Weight Percent Oil, Based on Asphalt Weight. Same as
procedure in 3 above.
10. AC-10+3.3 Weight Percent CLA+15 Weight Percent Tire Rubber+2
Weight Percent Oil, Based on Asphalt Weight. Same as 6 above but
with 15 weight percent tire rubber.
11. AC-20 meeting/LASHTO M226-80 Table II.
12. AC20+5 Weight Percent CLA, Based on Asphalt Weight. See
procedure outlined in 2 above.
13. 15 Pen Asphalt. Hard asphalt with 10-15 Pen at 77.degree.
F.
14. 15 Pen Asphalt+4 Weight Percent CLA, Based on Asphalt Weight.
See procedure outlined in 2 above.
15. 15 Pen Asphalt+5 Weight Percent CLA, Based on Asphalt Weight.
See procedure outlined in 2 above.
Each of these products was subjected to a series of tests to
determine properties related to asphalt product performance. These
tests are:
1. Viscosity (ASTM D-4957) at 60.degree. C. This test is used as an
indicator of relative stiffness or hardness of an asphalt cement at
a moderately high temperature to which a pavement might be expected
to be subjected. Viscosity at such temperature also frequently is
used as a specification by purchasers.
2. Viscosity (ASTM D-4957) at 135 .degree. C. This test is used as
an indicator of relative stiffness or hardness of an asphalt cement
at the highest temperature to which pavement might be expected to
be subjected.
3. Penetration (ASTM D-5) at 4 .degree. C. This test is an
indicator of relative stiffness or hardness of an asphalt cement at
low temperature. This, with a stiffness value at a higher
temperature, such as penetration at 25.degree. C., provides an
indicator of a temperature susceptibility of asphalt cements.
4. Penetration (ASTM D-5) at 25.degree. C. This test is an
indicator of relative stiffness or hardness of an asphalt cement at
moderate temperature. Penetration at 25.degree. C. is also
specified in ASTM specifications for asphalt cements by many
purchasers.
5. Ductility (ASTM D-113) at 4.degree. C. This test method provides
one measure of tensile properties of bituminous materials at low
temperatures. It also is used to measure ductility for some
polymer-modified asphalt cement specification requirements.
6. Softening point (AASHTO T-53) in degrees. Asphalt does not
change from the solid state to the liquid state at any definite
temperature, but gradually becomes softer and less viscous as the
temperature rises. For this reason, the determination of softening
point must be made by fixed, arbitrary and closely defined method
if the results obtained are to be comparable. Softening point is
indicative of the tendency of the asphalt to flow at elevated
temperatures encountered in service. Softening point also is used
in many purchasers' specifications for asphalt blends.
7. Float (ASTM D-139) in seconds. This is a measurement of the
ability of the asphalt to resist flow at 60.degree. C. A higher
number indicates that the non-Newtonian properties have been
achieved.
8. Penetration-Viscosity number (PVN). PVN was developed by McLeod
as an indication of temperature susceptibility of asphalt. The PVN
has become part of some asphalt specifications. By setting a
minimum value for PVN, an attempt is made to control the
temperature susceptibility of asphalt, especially excessive
hardening of asphalt in the low temperature range.
9. The viscosity aging index is a ratio of the RTFO 60.degree. C.
viscosity to the original 60.degree. C. viscosity indicating the
rate at which asphalt hardens. A lower number indicates that the
asphalt will age slower and resist cracking for a longer period of
time.
Table 1 presents the results of each of these tests on each of the
asphalt compositions 1 through 15:
TABLE 1
__________________________________________________________________________
TEST RESULTS ON ORIGINAL ASPHALT BLENDS Asphalt VIS @ VIS @ PEN @
PEN @ DUCT @ SOFTENING FLOAT, No. Description 60.degree. CPS
135.degree. C. CST 4.degree. C. DMM 25.degree. C. DMM 4.degree. C.
CM POINT, .degree.F. SEC. PVN
__________________________________________________________________________
1 AC-5 608 189 65 172 100+ 109 120 -.79 2 AC-5 + 3.3% 2,826 864 42
116 24 120 1,800+ 1.18 CLA 3 AC-5 + 10% TR + Separated - no test
data 2% Oil 4 AC-10 + 10% Separated - no test data TR + 2% Oil 5
AC-5 + 3.3% 2,000 509 62 123 33 115 1,800+ .42 CLA + 10% TR + 2%
Oil 6 AC-10 1,081 256 115 112 420 - .76 7 AC-10 + 2% CLA 1,794
1,200 81 10+ 1,800+ 1.16 8 AC-10 + 3.3% 3,210 1,310 22 75 122
1,800+ 1.18 CIA 9 AC-10 + 3.3% 2,489 606 31 67 10 120 1,800+ -.07
CLA + 10% TR + 2% Oil 10 AC-10 + 33% 18,963 *7,100 37 62 13 172
1,800+ 3.32 CLA + 15% TR + 2% Oil 11 AC-20 2,032 362 34 73 24 118
160 -.72 12 AC-20 + 5% CLA 35 165 1,800+ 13 15 PEN AC 15,000 11 140
14 15 PEN AC + 4% 14 **45 195 CLA 15 PEN AC + 5% 17 **21 235 CLA
__________________________________________________________________________
*Brookfield **Ductility at 25.degree. C.
Table 2 presents measurements for viscosity at 60.degree. C. and
135.degree. C., penetration at 4.degree. C. and 25.degree. C.,
ductility at 4.degree. C. and a viscosity aging index of the
asphalt after the Rolling Thin Film Oven Test ("RTFOT") prepared
from the same asphalts as in Table 1. RTFOT residues are prepared
from unaged asphalts that are artificially aged by applying heat
and air to a small amount of asphalt placed in a bottle that is
rotating in the rolling thin film oven. This test simulates the
aging that occurs due to the processing in the hot mix plant,
simulating the viscosity the asphalt will be at the time of
placement on the roadway.
TABLE 2
__________________________________________________________________________
MEASUREMENTS ON RTFOT RESIDUES Asphalt VIS @ VIS @ PEN @ PEN @ VIS
AGING DUCT @ No. Description 60.degree. C. PS 135.degree. C. CST
4.degree. C. DMM 25.degree. C. INDEX 4.degree. C.
__________________________________________________________________________
CM 1 AC-5 1.352 273 39 104 2.22 40 2 AC-5 + 33% CLA 5,23 1,066 20
78 1.93 10 3 AC-5 + 10% TR + 2% Oil Separated - no test data 4
AC-10 + 10% TR + 2% Oil Separated - no test data 5 AC-5 + 33% CLA +
10% TR + 2% Oil 5,260 646 45 90 2.63 16 6 AC-10 2,417 2.23 7 AC-10
+ 2% CLA 2,744 1.54 8 AC-10 + 3.3% CLA 5,280 1,120 16 9 AC-10 +
3.3% CLA + 10% TR + 2% Oil 5,340 760 23 50 2.15 3 10 AC-10 + 3.3%
CLA + 15% TR + 2% Oil 10,482 31 61 1.03 14 11 AC-20 4,869 468 24 54
2.35 9
__________________________________________________________________________
Asphalt modified with CLA exhibits improved properties in the
following areas:
1. reduced aging (aging ratio)
2. reduced temperature susceptibility (PVN)
3. improved high temperature performance (VIS 275, Float, Softening
Point)
4. improved cold temperature performance (Pen at 4.degree. C., 25
.degree. C.)
The data in Table 1 and Table 2 demonstrate, for example, that AC 5
modified with CLA is comparable in performance to the more
expensive AC 20 or AC 30, based on the Vis at 60.degree. C.
Comparing AC 5 plus CLA to AC 20 note the aging ratio, PVN,
kinematic viscosity, float, Pen at 4 .degree. C. and Pen at 25. the
aging ratio is lower, indicating improved aging. The PVN is more
positive, indicating reduced temperature susceptibility. The
kinematic viscosity is higher indicating better high temperature
properties. The float test indicates the asphalts' ability to
resist flow at high temperatures. The penetrations are higher
compared to asphalts with similar 60.degree. C. viscosities
indicating improved low temperature performance. The performance
improvements is further substantiated by the Rheometric data
contained in Table 3.
Asphalts further modified with tire rubber exhibit improvements to
the penetration at 4.degree. C., indicating improved
cold-temperature performance. As the tire rubber concentration is
increased, 10% to 15% (No. 6 vs. No. 7), viscosities increase
drastically and the PVN improves drastically. Further, the aged
ratio drops nearly to 1.0, showing the improvement to aging. Tests
were not able to be run on control samples with tire rubber and no
CLA, since the rubber does not stay in solution. All tire rubber
plus asphalt plus CLA passed 30 day stability tests showing that
the rubber is stable in the asphalt.
SHRP Binder Testing
SHRP, the Strategic Highway Research Program, was created by the
federal government to investigate new methods to specify asphalt
that would relate directly to pavement performance. Past methods
tried to use penetration or viscosity to control the stiffness of
the asphalt at various temperatures. These methods (called Pen
grading or viscosity grading) were empirical and did not relate
directly to pavement performance. SHRP is recommending that
asphalts be graded by considering the climatic conditions and the
loading conditions that the pavement will be subjected to SHRP
created the following rheometric tests which evaluate the asphalt
at various temperatures, aging conditions and loading conditions.
User agencies are just beginning to specify SHRP graded asphalts.
Very few suppliers can supply the grades at the extreme hot or cold
ends of the grading scale.
The SHRP test performed on the asphalt compositions of the present
invention are:
1. Dynamic Shear Rheometer (SHRP D-003). This test (abbreviated
"DSR") utilizes a rheometer to measure the dynamic shear modulus
or, or stiffness, of an asphalt cement. The stiffness properties of
asphalt binders at the upper range of service temperatures
determine, in part, the rutting resistance the asphalt binder
contributes to the hot mix asphalt (asphalt and aggregate). At
intermediate temperatures, the stiffness properties are related to
fatigue resistance of hot mix asphalt. In Table 3, the DSR
measurements for test samples are reported for "original DSR"
referring to the unaged asphalt compositions, as "RTOT DSR,"
referring to RTFOT samples of the asphalt compositions and as "PAV
RESID DSR" referring to pressure aging vessel samples of the
compositions prepared the following method: The PAV (pressure aging
vessel) residue is prepared by first subjecting the unaged asphalt
to the aging of the RTFO. The RTFO residue is then placed on round
trays and these trays are placed in the PAV vessel. The vessel is
then pressurized to 2,100 kilopascals for 20 hours at a temperature
of either 90.degree. C., 100 .degree. C. or 110.degree. C.
depending on the climatic region. This residue represents the aging
that the asphalt would receive after 8-10 years in the field.
2. Bending beam rheometer (SHRP B-002). This test, abbreviated
"BBR" in Table 3, utilizes a bending beam rheometer to measure the
low temperature stiffness of asphalt cements. The low temperature
stiffness should be less than a maximum value to minimize magnitude
of the thermal shrinkage stresses developed during pavement
cooling. Table 3 presents pressure aging vessel residual BBR
measurements for each of the asphalt compositions investigated as
both "S" units (MPA) at the indicated temperatures and as "M" units
(MPA) at the indicated temperatures.
3. SHRP grade. This measurement appearing as the last column in
Table 3 indicates the preferred high and low temperature units of
the resulting asphalt, in degrees Celsius. For example, the SHRP
grade PG 52-28 for AC-5 indicates a product recommended for use in
temperatures up to 52.degree. C. and as low as -28.degree. C.
TABLE 3
__________________________________________________________________________
SHRP BINDING TESTING ORIGINAL DST RTFOT DSR Asphalt G*/SINS,
G*/SINS, PAV RESID. DSR PAV RESID. BBR PAV RESID. BBR Description
KPA @ .degree.C. KPA @ .degree.C. G*/SINS, MPA @ .degree.C. S, MPA
@ .degree.C. M, MPA @ .degree.C. SHRP
__________________________________________________________________________
GRADE AC-5 1.40 @ 52.degree. C. 3.13 @ 52.degree. C. 2.82 @
16.degree. C. 165 @ -18.degree. C. 0.40 @ -18.degree. C. PG 52-28
AC-5 + 1.57 @ 64.degree. C. 2.61 @ 64.degree. C. 4.78 @ 18.degree.
C. 197 @ -18.degree. C. 0.38 @ -18.degree. C. PG 64-28 CLA AC-5 +
1.03 @ 64.degree. C. 2.23 @ 64.degree. C. 3.69 @ 10.degree. C. 217
@ -24.degree. C. 0.35 @ -24.degree. C. PG 64-34 CLA + 10% TR AC-10
+ 1.73 @ 64.degree. C. 3.05 @ 64.degree. C. 4.8S @ 16.degree. C.
188 @ -18.degree. C. 0.31 @ -18.degree. C. PG 64-28 CLA + 10% TR
AC-10 + 2.54 @ 64.degree. C. 3.36 @ 64.degree. C. 3.32 @ 16.degree.
C. 110 @ -18.degree. C. 0.35 @ -18.degree. C. PG 64-28 CLA + 15% TR
AC-20 1.10 @ 64.degree. C. 2.36 @ 64.degree. C. 3.62 @ 22.degree.
C. 173 @ -12.degree. C. 0.37 @ -12.degree. C. PG
__________________________________________________________________________
64-22
Most prior art asphalt cements required the addition of substantial
amounts of organic polymers such as styrene butidiene, styrene
butidiene styrene, ethylene vinyl acetate and others in order to
produce the performance characteristics required for high SHRP
ratings. However, reference to Table 3 shows that, for example, the
addition of the cross-linking agent of the present invention to a
standard AC-5 asphalt increases the high temperature SHRP rating by
two SHRP grades, from 52.degree. C. to 58.degree. C. to 64.degree.
C. Subsequent incorporation of 10 weight percent tire rubber
reduced the low temperature rating by a similar amount, one grade,
from -28.degree. C. to -34.degree. C. This produces a product equal
or better in quality and SHRP rating to, for example, an AC-20
asphalt which is produced utilizing a high polymer content and
would be much more expensive to produce than the AC-5 plus CLA or
AC-5 plus CLA plus tire rubber content asphalts of the present
invention. Comparing the results of Tables 1 and 2 to the SHRP
results of Table 3, one can see the effects of the CLA and TR more
clearly. The AC-5 viscosities have increased mirroring the SHRP
grade increases from PG-52 to PG-64. The low temperature properties
of the AC-5 are maintained and confirmed by the BBR results (see S
and M).
4. Roofing Asphalt. Table 1, Nos. 12-15 show the effect of CLA at
high percentages in two asphalts, AC-20 and hard 15 Pen asphalt.
ASTM D-312 classifies roofing asphalts by the softening point,
penetration and ductility. The softening point is used so that the
asphalt will resist flow on inclines during high temperatures. The
penetration and ductility are specified so that some resistance to
cracking after aging will be available. To meet ASTM D-312, the
current manufacturing method is to take light flux oils and air
blow the light flux oils oxidizing the flux, drMng off the light
fractions and hardening the flux meeting the desired D-312 grade.
Air blowing is time consuming, expensive and is becoming an air
quality restrictive operation. Permitting an air blowing still in
and near large cities is becoming very hard due to the tightening
of air quality laws. Table 1, No. 12 shows an AC-20 asphalt
modified with 5% CLA that meets ASTM D-312 Type I roofing
specifications. Table 1, No. 15 shows a 15 Pen asphalt modified
with 5% CLA meeting ASTM D-312 Type IV roofing specifications. Of
note is the very good ductility. Normal roofing asphalts barely
pass a 5 ductility.
The foregoing disclosure and description is illustrative only, and
various changes may be made in procedures, materials and
compositions, within the scope of the appended claims, without
departing from the spirit of the invention.
* * * * *